The objective of this proposal is to characterize properties of corpus luteum lysosomes and to determine how these properties are related to changes in luteal function. Emphasis will be placed on the role of lysosomal phospholipases in the metabolism of plasma membrane phospholipids. The properties of lysosomes to be characterized in the luteal tissue of superovulated immature rats are: (1) the total levels of several acid hydrolases; (2) the latency of these enzymes; (3) the distribution of lysosomes into subcellular particulate fractions following differential centrifugation and (4) the bouyant densities of lysosomes and their distribution into subpopulations on sucrose density gradients. Latency of lysosomal enzymes is determined by measurement of enzyme activities in the presence and absence of Triton X 100, and by measuring the rates of release of lysosomal enzymes from lysosome enriched fractions during spontaneous autolysis at 37 degrees. Protocols are designed to measure alterations for each of the above properties of lysosomes during the periods of corpus luteum growth, maturation and regression. Changes in lysosomal properties which occur following acute stimulation of luteal tissue will also be determined following systemic or local administration of gonadotropins, estrogens, corticoids, progesterone and prostaglandins. Phospholipase A1 and A2 activities of luteal lysosomes will be characterized with several synthetic lecithins which we have prepared in our laboratory. During those periods of luteal function, which are associated with the greatest differences in latency of lysosomal enzymes, plasma membranes will be prepared for characterization of their phospholipids. The membrane content of the classes of phospholipids and the composition and positional distribution of the phospholipid acyl moieties will be determined by procedures of TLC, selective hydrolysis of fatty acids with phospholipase A2 tranesterification of fatty acids and GLC. With these studies we hope to establish temporal relationships between hormone stimulus-lysosome activity-membrane structure and luteal cell function.